In recent years, there has been an increasing interest in the use of ceramics for structural applications historically served by metals. The impetus for this interest has been the superiority of ceramics with respect to certain properties, such as corrosion resistance, hardness, modulus of elasticity, and refractory capabilities when compared with metals, coupled with the fact that the engineering limits of performance of many modern components and systems are now gated by these properties in conventionally employed materials. Examples of areas for such prospective use include engine components, heat exchangers, cutting tools, bearings and wear surfaces, pumps, and marine hardware.
Current and past efforts at producing higher strength, more reliable, and tougher ceramic articles have largely focused upon (1) the development of improved processing methods for monolithic ceramics and (2) the development of ceramic matrix composites. A composite structure is one which comprises a heterogeneous material, body or article made of two or more different materials which are intimately combined in order to attain desired properties of the composite. For example, two different materials may be intimately combined by embedding one in a matrix of the other. A ceramic matrix composite structure typically comprises a ceramic matrix which incorporates one or more diverse kinds of filler or preform materials such as particulates, fibers, rods or the like.
Many of the past difficulties in forming desirable materials have been overcome by the methods described in several commonly owned patents and copending patent applications. These commonly owned patents and patent applications are discussed below.